Organic electroluminescent (EL) devices, consisting of thin layers of organic molecules sandwiched between transparent and metallic electrodes, are ideal candidates for use in display applications since they are inexpensive to fabricate and capable of a full range of colors.
In the prior art, a class of organic EL devices that have exhibited high efficiency and good stability, are those based on metal complexes of 8-hydroxyquinoline and its derivatives (Vanslyke et al. U.S. Pat. No. 4,539,507; 5,150,006). The emission of colors ranging from blue to red has been achieved by different dye doping of the metal complexes. However, light emitting devices (LED) based on the prior art dye doped metal complexes have limited current carrying capability, which curtails the brightness of the resulting devices. This is especially true when the prior art dye doped metal complexes are used in light emitting devices (LED) designed to emit in the blue range. For example, a prior art LED with an emission maximum at 470 nm produced approximately 1300 cd/m.sup.2 at 15 volts of operating voltage.
It is a purpose of this invention to provide a class of new organometallic complexes for use in light emitting devices.
It is another purpose of this invention to provide preparation methods for the disclosed organometallic complexes for use in light emitting devices.
It is still another purpose of this invention to fabricate light emitting devices with the disclosed organometallic complexes.
It is yet another purpose of the present invention to provide light emitting devices with high brightness.
It is a further purpose of the present invention to provide light emitting devices for emission in the blue range with improved efficiency.